Aftertreatment systems, for treating emissions of an engine, are well known in the art. An aftertreatment system typically includes a diesel particulate filter (DPF) in addition to other emission treatment catalyst such as a diesel oxidation catalyst and/or a nitrous oxide reduction catalyst. The DPF filters particulate matter present in exhaust gas of the engine.
The particulate matter trapped in the DPF is removed periodically by regeneration. Regeneration may involve using a heat source (not shown) to combust the particulate matter. The residual matter, present in the DPF after combustion, may have to be removed regularly. The removal of the residual matter may involve a recurring maintenance cost and down time. Further, the DPF may also have to be replaced regularly.
The DPF is typically provided to conform to emission requirements in certain jurisdictions. However, other jurisdictions may have less strict emission requirements such that the DPF is not an essential component for treatment of exhaust gas. In such jurisdictions, the DPF may therefore entail avoidable maintenance and/or replacement costs. However, when the DPF is removed, the engine noise becomes too high which is undesirable.
U.S. Pat. No. 6,892,854 discloses muffler assembly having an upstream sound attenuating region, a downstream sound attenuating region, and a catalytic converter region between the upstream and downstream sound attenuating regions. The upstream sound attenuating region includes flow distribution arrangement to direct the exhaust gas through the catalytic converter region. Although, the patent discloses a combined muffler and catalytic converter arrangement, the patent does not disclose retrofitting of a sound attenuating arrangement in an exhaust after-treatment system.